The present invention relates generally to the field of substrate processing for semiconductor manufacturing and, more specifically, to an apparatus and a method that improve uniformity of deposition or etching of films on the substrate by providing bi-directional gas flow.
An important part of integrated circuit manufacturing is the processing of the semiconductor substrate in which active devices such as transistors and capacitors that comprise the integrated circuits are formed. Processing of the substrate includes, for example, growth of an epitaxial silicon or polysilicon layer or film, the formation of a thermal oxide or thermal nitride layer over silicon, or etching of portions of previously deposited layers. These exemplary processes, among others, are typically performed in thermal deposition or etch process chambers. Process chambers typically include a platform such as a susceptor or an edge ring, a substrate support mechanism, a quartz housing or cover, and heat lamps that provide heat energy to the substrate being processed.
Deposition and etching are typically performed in these types of chambers by flowing a process gas through the chamber and over the substrate, which is resting on the platform in the chamber. The substrate and the process gas are heated during the processing. The gas includes the chemical species that react at the wafer surface to deposit or etch the layers of material on the substrate. The process chamber typically includes a gas inlet port and a gas outlet port.
Deposition and etch process chambers are normally designed such that the process gas flows over the substrate and from one side of the chamber to the other. The chemical species react at the wafer surface, which results in a change in gas composition (i.e., depletion of the gas species) in the direction of gas flow. For this reason, some chambers are provided with a mechanism to rotate the wafer holder that carries the substrate so that the reaction rate at the surface of the substrate is averaged out to provide uniformity of deposition or etching along the entire surface. Another technique that is an attempt to achieve greater uniformity of deposition or etching by overcoming the depletion phenomenon is to inject the gas stream into the chamber such that a mixing of the gas occurs which averages out the deposition or etch rate. Another technique is to tilt the wafer support, which allows xe2x80x9cfreshxe2x80x9d gas to arrive at the wafer surface as the gas travels across the wafer.
FIG. 1A shows an example of a chamber 100 that can be used to process semiconductor substrates. Chamber 100 includes an enclosure 101 that has a top housing 102 and a bottom housing 104, which are typically made of quartz. Platform 110 is located within the chamber 100. Platform 110 typically defines a pocket (not shown) for holding a semiconductor substrate (not shown) to be processed. Lamps 106 are located outside of the top housing 102 and the bottom housing 104. Lamps 106 are typically arranged in an array (not shown). Lamps 106 provide heat energy to the chamber, and thus to the substrate, during processing of the substrate. Pyrometers 108a and 108b are positioned above and below enclosure 101. Pyrometer 108a measures the temperature of the substrate being processed, while pyrometer 108b measures the temperature of the platform 110 on which the substrate rests. Platform 110 is supported by platform support 112. Platform support 112 is typically configured so that it can rotate the platform 110 during processing of the substrate. Substrate lift pins 114 are located below the platform 110 and extend upwardly through apertures (not shown) in platform 110. Substrate lift pins 114 lift the substrate either at its edge or at its bottom surface during loading and unloading of the substrate into and out of the chamber.
As shown in FIG. 1B, chamber 100 includes a base ring 103 surrounding enclosure 101. Base ring 103 can be generally rectangular in shape with the circular enclosure 101 having a dome-shaped top housing 102 mounted within base ring 103. Referring again to FIG. 1A, a gas inlet 150 and a gas outlet 160 are usually provided at diametrically opposed locations on base ring 103. Arrows 116 illustrate the direction of the gas flow across the platform 110 from gas inlet 150 to gas outlet 160. A clamp ring 105 can be provided to seal the top housing 102 to the base ring 103. A second damp ring 107 can be provided to seal the bottom housing 104 to the base ring 103.
Because the process gas of chamber 100 flows in one direction, the substrate being processed must be rotated to average out the depletion or etch rate of the gas as it travels across the substrate in the direction of arrows 116. Platform 110 is typically rotated as it carries the substrate. Platform support 112 includes an axle 113 that is connected to a motor (not shown) to provide the rotation. A rotating platform adds complexity and cost to the chamber 100 because the substrate must remain as level as possible as it rotates so as to achieve a uniform deposition or etch rate. Any wobbling or eccentricity of the platform 110 can result in uneven deposition or etching, which can ultimately result in waste of a substrate. Processing chamber 100 can be greatly improved by eliminating sources of potential error in the process such as the mechanisms that rotate the substrate and platform 110.
In one embodiment, a semiconductor substrate processing chamber includes an enclosure having a first junction and a second junction. A first gas inlet port is at the first junction. A first gas outlet port is at the second junction. A second gas inlet port is also at the second junction, and a second gas outlet port is at the first junction.
The first gas inlet port and the first gas outlet port cooperate to provide gas flow in a first direction, while the second gas inlet port and the second gas outlet port cooperate to provide gas flow in a second direction.